Diabetic retinopathy is a major neurovascular secondary complication of diabetes affecting the retina. There are no approved pharmacological therapies for prevention or treatment of DR. The pathophysiology sequella of DR is still undetermined, however research into neural deficits and blood-retinal barrier breakdown in the retina is advancing rapidly and suggest that neuronal anatomical changes and dysfunction precede vascular changes. Recent studies have identified impaired mitochondrial function in whole retinas and retinal endothelial cells with diabetes correlating to endothelial cell apoptosis and the breakdown of the blood-retinal barrier, but mitochondrial dysfunction of the neural retina has not been examined specifically. Neuronal mitochondria are potentially especially sensitive to metabolic disruption, and synaptic mitochondrial populations that provide local ATP production and calcium buffering may be especially prone to damage. Previously, we and others have demonstrated loss of retinal synapses and neuronal apoptosis with diabetes. We hypothesize that decreased synaptic mitochondrial genomic maintenance and impaired mitochondrial function in retinal neurons contributes to synapse loss and eventually neuronal apoptosis. In Aim 1, we propose to investigate mitochondrial genomic maintenance in a rat model of type-1 diabetes in both synaptic and somatic retinal fractions for mtDNA copy number and heteroplasmy (deletions and mutations) assessment. Using a novel absolute quantitation method of mtDNA copy number and next generation sequencing to assess heteroplasmy and mtDNA mutation rates we will comprehensively determine alterations to the mtDNA genome. In Aim 2, changes in neural retina mitochondrial function with diabetes will be investigated through measuring oxygen consumption rates of isolated retinal synaptosomes from the same animal model from Aim 1. Additionally, qualitative staining of mitochondrial membrane potentials as a surrogate for activity in order to localize mitochondrial activity in situ will be carried out. Identification of mitochondrial defects in genomic maintenance and function will provide targets for future investigations of disease mechanisms involved in DR, as well as targets for drug development and further insight to the DR disease progression. Additionally, these proposed studies will be beneficial in identifying the retinal neuronal mitochondria as a contributing facto to the progression of diabetic retinopathy.